The present invention relates generally to the field of electrically-driven reciprocating pumps. More particularly, the invention relates to a pump which is particularly well suited for use as a fuel pump, driven by a drive assembly employing permanent magnets and a solenoid coil to produce pressure variations in a pump section and thereby to draw into and express from the pump section a fluid, such as a fuel being pumped.
A wide range of pumps have been developed for displacing fluids under pressure produced by electrical drives. For example, in certain fuel injection systems, fuel is displaced via a reciprocating pump assembly which is driven by electric current supplied from a source, typically a vehicle electrical system. In one fuel pump design of this type, a pump and nozzle assembly includes a drive section and a pump section. The drive section includes a drive assembly that is energized by the electric current to provide motion to the pump section to cause the pump section to pump the fuel. The drive assembly is held in a fixed position within a drive section housing and includes one or more permanent magnets, with an electrical coil surrounding the permanent magnets. The electrical coil is wound about a coil bobbin and is movable in a reciprocating motion by the energizing and de-energizing by the electrical signals and transmits that reciprocating motion to the pump section by a drive member that is affixed to the coil bobbin. The reciprocating motion of the drive member is transmitted to a plunger assembly comprised of a plunger that is in contact with the drive member and which extends into a pump chamber where the fluid is drawn into the pump chamber and expelled therefrom by the motion of the plunger assembly. As such, the reciprocal movement of the drive member causes the plunger assembly to pump the fluid from the pump chamber for use in a combustion chamber.
One problem, therefore, in the construction of the plunger assembly is to make the plunger assembly of a small length so as to reduce the overall size of the components of the pump.
There is a need, therefore, for an improved technique for constructing a plunger assembly for use in a fluid pump wherein the assembly is dimensionally reduced in length to produce a more compact, smaller construction of an internal combustion engine.